Ishikawa, Tetsuo

Kobayashi, Yosuke

Kovács, Tibor

Tokonami, Shinji

Yoshinaga, Shinji

English

Shinji TOKONAMI

Tibor KOVÁCS

Shinji YOSHINAGA

Yosuke KOBAYASHI

Tetsuo ISHIKAWA

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Japanese Journal of Health Physics

210Po and 210Pb Inhalation Dose by Cigarette Smoking in Gansu and Yunnan Provinces, China

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I INTRODUCTIONNowadays lung cancer is one of the most common kinds ofcancer in the world. The first cause of lung cancer is consid-ered as smoking, which accounts for almost 90% of lung can-cer deaths1). The carcinogenic effect of smoking has been wellestablished by both animal experiments and epidemiologicalsurveys.2, 3)Epidemiological studies on underground miners demon-strate that inhaling a large quantity of radon (222Rn) and itsprogeny also causes lung cancer.4) However, lung cancer risksassociated with exposure to low-level radon remain uncertain.Large-scale epidemiological surveys were carried out in Chinain order to assess the lung cancer risk associated with residen-tial radon,5, 6) and with radon in underground tin mines.7)However, the surveys carried out at that time are probablyopen to criticism from the viewpoint of dosimetry. First of all,in the aspect of radiation dose originating from radon, wefound that the presence of thoron (220Rn) is not negligible inthe area surveyed.8, 9) In the previous surveys, the detector sig-nal resulted from thoron was considered as the signal resultedfrom radon, because their radon detectors could not distin-guish thoron from radon. It was, therefore, expected that theradon detectors used in their surveys were considerably affect-ed by the presence of thoron. This leads that the radon con-centration was significantly overestimated with their radondetectors. Thus, we started a new survey a few years ago in order toestimate more reliable dose using our radon-thoron discrimi-native detectors10) and thoron progeny monitors.11) In this sur-vey, we have made efforts to re-estimate the doses due tomajor sources of natural radiation, including radon/thoronprogenies and gamma rays.8, 9) It was also expected that smok-ing causes significant dose in the studied area, because tobac-co smoke contains a significant quantity of naturally occurringradionuclides12) in addition to a considerable quantity of toxicchemical compound.13)In particular, 210Po and its parent nuclide 210Pb can befound in high activity concentration.14) 210Po and 210Pb are themembers of the uranium decay series and relatively long livedradionuclides. The half-life of 210Po is 138 days and that of210Pb is 22 years. These radionuclides might give a significantdose to humans. Thus, the dose due to inhalation of 210Po and210Pb in cigarettes has been studied in several countries.15～ 19)The UNSCEAR20) reports also indicated that 210Po is estimat-ed to cause about 7% of the internal dose from naturallyoccurring radionuclides.In this work, the 210Po and 210Pb activity concentrations ofdifferent sorts of cigarettes traded in our epidemiological sur-vey area (Gausu and Yunnan provinces, China) were exam-ined as a part of our dose re-estimation study. The annualeffective dose was estimated for a regular smoker due to theinhalation of these radionuclides.II MEASUREMENTS AND METHODS1.  SamplingIn the present study, 210Po and 210Pb concentrations weredetermined for 7 brands of cigarettes in China (available inGansu and Yunnan provinces). The locations of the twoJpn. J. Health Phys., 43 (2), 131 ― 134 (2008)Note210Po and 210Pb Inhalation Dose by Cigarette Smoking in Gansuand Yunnan Provinces, ChinaShinji TOKONAMI,*1 Tibor KOVÁCS,*2 Shinji YOSHINAGA,*1 Yosuke KOBAYASHI*1 and Tetsuo ISHIKAWA*1KEY WORDS: polonium, lead, inhalation, cigarette, smoking, China, dose.*1 National Institute of Radiological Sciences, 4 ― 9 ― 1 Anagawa,Inage-ku, Chiba 263 ― 8555, Japan.*2 Dept. of Radiochemistry, University of Pannonia, P.O. Box 158,8201 Veszprém, Hungary.Corresponding author: Tetsuo ISHIKAWA, E-mail: tetsuo_i@nirs.go.jp Fig. 1 The location of Gansu and Yunnan provinces. 132 Shinji TOKONAMI, Tibor KOVÁCS, Shinji YOSHINAGA, Yosuke KOBAYASHI and Tetsuo ISHIKAWAprovinces are shown in Fig. 1. The cities where the tobaccosamples were collected are shown as dotted circles. Thenames of brands collected are: Happiness, Stone forest, ScarletCamelia, Yun Yan from Yunnan province and Lhan Zhyou(red), Lhan Zhyou (brown), Haiyang from Gansu province.Also, as home-grown tobacco is very popular in these areas,these samples (pouch) were also collected in both provinces. The samples were purchased in 2006. The data on the ciga-rette samples including the tar, CO (carbon monoxide) andnicotine concentrations are shown in Table 1.2.  210Po and 210Pb concentration measurementOur measurement procedure, including sample preparation,is similar to that used in previous studies.15, 19) An outline ofthe measurement procedure is described below.(1) Leaching A known activity of 209Po tracer (17 mBq) was added as aninternal tracer to 2 g of air-dry tobacco sample. The sampleswere dissolved using three portions of 20 ― 30 mL concentrat-ed HNO3. After that, the samples were heated (evaporated) tonear dryness. In order to totally digest organic materials, a fewdrops of concentrated H2O2 were carefully added. Afterwards,three portions of 20 ― 30 mL concentrated HCl were added andevaporated to near dryness. Finally, 100 mL of 0.5 M HClstock solution was prepared from the residue.(2) Source preparation Polonium was deposited spontaneously onto high nickel-con-tent stainless steel disc for 3 hours at 80°C, 100 mg ascorbicacid was added to reduce Fe3+. The deposition efficiency wasbetween 85 ― 90%. Two sources were prepared as stock solu-tions. After drying, the surfaces of the disc were measured inambient temperature using an alpha spectrometer equippedwith a semiconductor silicon detector.The applied alpha spectrometer was a Canberra Model7401 type alpha chamber equipped with 19 keV resolutionPIPS detector. Fig. 2 shows an example of alpha spectrum. Ascan be seen, the peak for 210Po (5.30 MeV) does not overlapwith that for 209Po (4.88 MeV). Thus, it was assumed that209Po has little effects on the 210Po measurement. The mini-mum detectable activity (95% confidence level) for the spec-trometer was estimated to be 0.67 mBq/g with a counting timeof 80,000 sec. The mean yield of the measurement was 55%and this is mainly due to the loss generated during the evapo-ration. (3) Determination of the 210Pb concentration Our previous study19) showed that the 210Po and 210Pb iso-topes are in radioactive equilibrium due to the long storageand fermentation period. Therefore, 210Po was assumed to bepresent in the same concentration as its parent nuclide (210Pb)for the following calculations.III RESULTS AND DISCUSSION1.  210Po and 210Pb concentration measurementTable 1 shows the 210Po (210Pb) activity concentrations ofthe examined cigarette types. Apparently, the measured 210Poactivity concentration values were between 17.4±3.4 and27.2±3.2mBq/g.The activities of the cigarettes from Yunnan Province(Happiness, Stone forest, Scarlet Camelia, Yun Yan) were alittle bit higher (30%) than those from Gansu Province. Theresults of this study were in the range of values reported from Energy (keV) 3327.9 4176.53752.2 4600.7 5025.0 5873.65449.3 6297.8 6722.1 7146.4 CountsFig. 2 An example of alpha spectrum obtained from thesample measurement.Province BrandNicotine Tar[mg] CO 210Po 210Po[mg] [mBq] [mBq/g] [mBq/cigarette]Lhan Zhyou12 0.8 13 17.6±3.4 11.3±2.2(red)GansuLhan Zhyou13 0.9 13 17.4±3.5 11.1±2.3(brown)Haiyang 13 0.9 13 24.3±3.4 15.5±2.3Tobacco-pouch － － － 17.8±4.2 －Happiness 15 1.2 15 22.8±4.1 14.7±2.3Stone forest 14 1.2 15 27.2±3.2 18.3±2.5Yunnan Scarlet Camelia 14 1.3 15 22.9±3.3 14.7±2.2Yun Yan 14 1.2 15 26.0±3.5 16.7±2.2Tobacco-pouch － － － 18.9±4.1 －Table 1 Activity concentration of 210Po and 210Pb (mBq/cigarette) in cigarette samples210Po and 210Pb Inhalation Dose by Cigarette Smoking in Gansu and Yunnan Provinces, China 133other countries.15～ 19)2.  Dose estimationThe dose caused by 210Po and 210Pb in cigarette smoke wascalculated under the following assumptions. These assump-tions were as the same as those in our previous study.19) As adaily consumption rate of cigarettes, a value of 20 cigarettes/daywas used; this enables us to compare our work with previousworks easily. In the case of tobacco pouch (home-growntobacco), the same consumption rate and an average weight of0.65 g/cigarette were assumed. According to recent publications,15, 17) 70% of the poloniumin a cigarette was assumed to be transferred into the cigarettesmoke. Although the transfer factor might be different fromcigarette to cigarette, it was assumed to be the same for allbrands of cigarettes. For the dose calculation, the ratio ofinhaled smoke to totally produced smoke is needed. The ratiowas assumed to be 50% on the basis of recent references15, 17).As for the dose conversion factors for adults20), 3.3×10 ― 6 Sv/Bq and 1.1× 10 ― 6 Sv/Bq were used for the inhalation of210Po and 210Pb, respectively. Considering the above assumptions, the annual effectivedose (Sv) due to the inhalation of 210Po or 210Pb by smoking(E) can be calculated with the following formula. E = F1F2KGCT (1)where F1 is the average transfer factor from tobacco tosmoke (0.7), F2 is the ratio of inhaled smoke to totally pro-duced smoke (0.5), K is the dose conversion factor for 210Poor 210Pb (Sv/Bq), G is the number of cigarettes smoked (20cigarettes/day), C is the concentration of 210Po or 210Pb(Bq/cigarette), and T is the duration of dose calculation (365days).Table 2 shows the annual effective dose due to 210Po and210Pb inhalation via smoking (20 cigarette/day). The averageannual effective dose was estimated to be 123.2±22.3μSv/yand 41.1±7.4μSv/y for 210Po and 210Pb, respectively. The range of estimated dose was 93.5 ― 154.3μSv/y for210Po and 31.2 ― 51.4μSv/y for 210Pb. The average dose origi-nating from the two isotopes was 164.3±23.5μSv/y. IV CONCLUSIONIn the present study, the 210Po and 210Pb activity concentra-tions in Chinese cigarettes were investigated for 7 brandsavailable in the market and for 2 samples of home-growntobacco. The 210Po activities of cigarettes were between 11.1±2.2 and 18.3±2.5 mBq/cigarette. As we expected, these val-ues were comparable to the range reported in previous litera-tures.15～ 19)The activity values of cigarette samples originating fromYunnan province were approximately 30% higher, whichenhances radiation dose received due to smoking. The annualeffective dose originating from 210Po in cigarettes was withina range of 93.5 ― 154.3μSv/y and that from 210Pb was within arange of 31.2 ― 51.4μSv/y, in the case of smoking one pack ofcigarettes (20 cigarettes) a day. The radiation dose received during smoking was consideredto be of a small scale, compared with the dose from radon/thoronand their progenies. However, it is desirable for our epidemio-logical study to consider doses from major sources of naturalradiation. In this point of view, the estimation of dose due tosmoking was significant. In the future, by the measurement ofsamples of cigarettes available in the market, we would like toget a rather comprehensive picture on the radiation dose dur-ing smoking for the people living in these two provinces.REFERENCES1) Centers for Disease Control and Prevention (CDC);Reducing tobacco use: a report of the surgeon general,S/N 017-001-00544-4 (2000).2) S. S. HECHT; Tobacco smoke carcinogens and lung can-cer, J. Natl. Cancer Inst., 91, 1194 ― 1210 (1999).effective dose effective doseProvince Brand (μSv/y) from (μSv/y) from210Po 210PbLhan Zhyou (red) 95.4 31.8GansuLhan Zhyou (brown) 93.5 31.2Haiyang 131.1 43.7Tobacco pouch (Gansu) 97.6 32.5Happiness 123.8 41.3Stone forest 154.3 51.4Yunnan Scarlet Camelia 123.6 41.2Yun Yan 140.7 46.9Tobacco pouch (Yunnan) 103.8 34.6Mean value±σ 123.2±22.3 41.1±7.4Minimum value 93.5 31.2Maximum value 154.3 51.4Table 2 The annual committed effective dose due to 210Po and 210Pb inhalation via smoking (20cigarettes per day)134 Shinji TOKONAMI, Tibor KOVÁCS, Shinji YOSHINAGA, Yosuke KOBAYASHI and Tetsuo ISHIKAWA3) International Agency for Research on Cancer, WorldHealth Organization (WHO); Tobacco smoke and invol-untary smoking, IARC monographs on the evaluation ofcarcinogenic risks to humans, volume 83 (2002).4) Committee on the Biological Effects of IonizingRadiations (BEIR); Health effects of exposure to indoorradon, BEIR VI (1999).5) W. J. BLOT, Z. Y. XU, J. D. 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ULATOWSKI, D. I. STRUMINSKA and A.BORYLO; Inhalation of 210Po and 210Pb from cigarettesmoking in Poland, J. Environ. Radioact., 57, 221 ― 230(2001). 16) G. HIROMOTO and A. C. PERES; Evaluation of 210Pb and210Po in cigarette tobacco produced in Brazil, J. Environ.Radioact., 62, 115 ― 119 (2002).17) A. E. M. KHATER; Polonium-210 budget in cigarettes, J.Environ. Radioact., 71, 33 ― 41 (2004).18) D. DESIDERI, A. MELI, L. FEDUZI and C. ROSELI; 210Poand 210Pb inhalation by cigarette smoking in Italy, HealthPhys., 92, 58 ― 63 (2007).19) T. KOVÁCS, J. SOMLAI, K. NAGY and G. SZEILER; 210Poand 210Pb concentration of cigarettes traded in Hungaryand their estimated dose contribution due to smoking,Radiat. Meas., 42, 1737 ― 1741 (2007).20) United Nations Scientific Committee on the effects ofatomic radiation (UNSCEAR); Source and effects of ion-izing radiation, UNSCEAR 2000 Report to the GeneralAssembly, with Scientific Annex (2000).Shinji TOKONAMISection Head, Environmental RadioactivitySurvey Section, Department of AdvancedTechnologies for Radiation ProtectionResearch, Research Center for RadiationProtection, National Institute of RadiologicalSciences. Visiting Professor of Chiba UniversityGraduate School and Tokyo MetropolitanUniversity. Speciality; 1) environmental monitoring on radon andthoron. 2) Relevant environmental dosimetry. Doctor’s degree inapplied physics from Waseda University.

1) Centers for Disease Control and Prevention (CDC); Reducing tobacco use: a report of the surgeon general,

effective dose effective dose Province Brand (ЖSv/y) from (ЖSv/y) from 210Po 210Pb Lhan Zhyou (red)

(210)Po and (210)Pb Inhalation Dose by Cigarette Smoking in Gansu and Yunnan Provinces, China

(210)Po and (210)Pb Inhalation Dose by Cigarette Smoking in Gansu and Yunnan Provinces, China

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